Abstract : This paper introduces some of the results of an empirical field study within a large technical system (high pressure gas transmission network), exploited by one company, in which safety results from a combination of anticipation and resilience obtained by a 'mixture' of individual expertise, team coordination and organisational context favouring the tasks carried out at the 'sharp end'. High pressure gas transmission presents itself as a network of pipelines for which one threat are 'external aggressions', such as damages occurring when tractors dig, for instance, trenches for civil, municipal or urban engineering projects. In a first section, some elements of definition of 'large technical system' (LTS) is provided; it introduces some of the specific features met in these types of systems. In a second section, after a presentation of the methodological and theoretical elements, a description of the safety measures designed within this LTS for prevention of external aggression is offered. In a third section, a first and heuristic (for further developments) model of resilience, inferred from observations and interviews, and inspired from the literature on 'macro cognition' and 'collective mindfulness' is presented. Finally, in a last section, some thoughts about the translation from description to action ('engineering') of resilience (whether creating, maintaining or improving resilience) are suggested.